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English: How crater-depth is measured, using the side-view of a typical crater. Depth "A" measures from the surface to the bottom of the crater. Depth "B" measures from the mean height of the rim to the bottom of the crater.
The depth of an impact crater in a solid planet or moon may be measured from the local surface to the bottom of the crater, or from the rim of the crater to the bottom. Crater depth diagram. The diagram above shows the full (side) view of a typical crater. Depth "A" measures from the surface to the bottom of the crater.
A central-peak crater is the most basic form of complex crater. A central-peak crater can have a tightly spaced, ring-like arrangement of peaks, thus be a peak ring crater, though the peak is often single. [3] Central-peak craters can occur in impact craters via meteorites. An Earthly example is Mistastin crater, in Canada. [1]
A diagram of a Subglacial eruption. (key: 1. Water vapor cloud 2. Crater lake 3. Ice 4. Layers of lava and ash 5. Stratum 6. Pillow lava 7. Magma conduit 8. Magma chamber 9. Dike) Click for larger version. Subglacial eruptions are a type of volcanic eruption characterized by interactions between lava and ice, often under a glacier.
Valhalla Basin on Jupiter's moon Callisto, taken by Voyager 1. A multi-ringed basin (also a multi-ring impact basin) is not a simple bowl-shaped crater, or a peak ring crater, but one containing multiple concentric topographic rings; [1] a multi-ringed basin could be described as a massive impact crater, surrounded by circular chains of mountains [2] resembling rings on a bull's-eye.
A complex crater, caused by collision of a hypervelocity body with another larger than itself, is typified by the presence of a dome at the centre of the site of impact. These domes are typically large-scale (on the magnitude of tens of metres) and thought to be the result of post-impact weakening of the overlying strata and basement.
The EID lists fewer than ten such craters, and the largest in the last 100,000 years (100 ka) is the 4.5 km (2.8 mi) Rio Cuarto crater in Argentina. [2] However, there is some uncertainty regarding its origins [ 3 ] and age, with some sources giving it as < 10 ka [ 2 ] [ 4 ] while the EID gives a broader < 100 ka.
An explosion crater is a type of crater formed when material is ejected from the surface of the ground by an explosion at or immediately above or below the surface. Stylised cross-section of a crater formed by a below-ground explosion. A crater is formed by an explosion through the displacement and ejection of material from the ground.